Certain devices, particularly complementary metal oxide semiconductor (CMOS) transistors, have very low power requirements while in stable bi-level states, but draw substantial through current while undergoing transitions between the states. These well known CMOS characteristics are described in numerous publications, for example the National Semiconductor Corporation Handbook entitled MM54HC/74HC High-Speed CMOS Family Databook. Because of these characteristics, CMOS devices have been used in the past in portable devices having low output power requirements from batteries over long time intervals, such as six months. For example, CMOS circuitry is employed in the relaxation oscillator of a commercial flea repelling device, basically disclosed in the co-pending, commonly assigned application of Bianco et al, Ser. No. 742,232, filed June 7, 1985 now U.S. Pat. No. 4,669,424.
The flea repelling device includes a low duty cycle relaxation oscillator including CMOS gating devices which drive an ultrasonic frequency oscillator through a CMOS gate. The oscillator is connected to a electric-compressional wave transducer. The low frequency and duty cycle, as well as the ultrasonic frequency supplied to the transducer, cause compressional waves to be emitted by the transducer. The compressional waves incident on the fleas repel the fleas. The oscillators and gate are powered by a pair of series-connected batteries, preferably lithium cells, which have a life of about six months. The prior art device is mounted in a housing carried by a collar on a domestic animal, such as a dog or a cat, from which fleas are to be repelled. The ultrasonic compressional waves derived by the transducer are reflected from the ground beneath the animal back to the body of the animal. While the prior art device has functioned admirably for its intended purpose, it is desirable to reduce the power requirements of the device, to reduce the size and weight of the housing and its contents, as well as to increase the life of the battery.
It is, accordingly, an object of the present invention to provide a new and improved portable, battery-powered oscillating device having low input power requirements.
Another object of the present invention is to provide a new and improved portable, battery-powered oscillating device having long life even though it uses batteries of small size and energy ratings.
A further object of the invention is to provide a new and improved portable electronic flea repelling device for emitting compressional waves with appreciably smaller energy battery requirements than prior art devices for the same purpose.
A problem in the manufacture of the prior art commercial electronic flea collar is that it is very component sensitive. If certain components, particularly the transducer, originate from different supplies, the circuit must frequently be redesigned to enable oscillations at the optimum ultrasonic frequency to be obtained. Different transducers have different characteristics and impedances and provide different impedance matches to the driving circuit. It has been found that this problem arises because the transducer is connected in a feedback circuit that is part of the ultrasonic frequency oscillator.
It is, therefore, a further object of the invention to provide a new and improved portable electronic flea repelling device having high efficiency, and is not particularly component sensitive.
A further object of the invention is to provide a new and improved electronic flea repelling device wherein electric-compressional wave transducers from different suppliers can be employed without any redesign of the circuitry which drives the transducer.